The present invention relates to a technique for recording and/or reproducing digital signals onto and/or from a record medium, a technique for transmitting and/or receiving digital signals, and a recording medium having digital signals recorded thereon.
As is to be appreciated, there is an ever increasing need to record and/or reproduce, transmit and/or receive, or otherwise handle a relatively large volume of information at a relatively high rate. In an effort to increase such handling capacity, main signals (such as digital video or audio signals) to be recorded or transmitted may be compressed. Additionally, such handling capacity may be further improved by minimizing the amount of non-main data. That is, the addition of non-main or other digital information may increase the amount of data which is to be recorded on a recording medium or transmitted by way of a transmission medium or the rate at which the main signals are recorded/reproduced or transmitted/received.
Although minimizing non-main data may be desirable, situations may arise wherein non-main data or other digital information should be added to the main signals. For example, a non-main signal may be added to the main signals so as to discourage or prevent unauthorized copying of video, audio or data signals or the like, as more fully described below.
More specifically, recording media for optically recording digital video signals, digital audio signals, computer program data or other information signals, such as the so-called compact disc (CD) for music or the CD-ROM for data recording, are currently in widespread use. Recently, progress is proceeding to make a so-called digital video disc (DVD) the next generation of recording medium. Audio or video signals recorded on a recording media (such as a CD, CD-ROM or DVD) may be reproduced by a reproducing apparatus and copied onto a recordable/reproducible recording medium (such as a hard disc). Thereafter, the data copied on the hard disc may be supplied to an encoder system, such as CD, CD-ROM or DVD type system, so as to produce a new CD, CD-ROM or DVD having the same signals as the original signals. Such new or copied recording media may be substantially identical to the originally recorded signals. Accordingly, it may be difficult to determine whether the signals recorded on a recording medium are the original signals or copied signals. Similar difficulties may also occur with other types of recording medium, such as with a tape-type recording medium and so forth.
In an effort to prevent the use of unauthorized copying of original audio, video, data or other types of signals, it may be desirable to determine or identified whether the signals recorded on various types of recording media are original signals or copied signals. (That is, it may be desirable to determine the so-called hysteresis of the recording medium.) One technique of providing an indication as to whether the recorded signals are originally recorded signals or copies thereof is to record information at a specified area on the recording medium which indicates that the respective recording medium has original signals or copied signals recorded thereon. However, this technique may utilize an area on the recording medium to record such indication information which may otherwise be used to record video, audio or data signals. As is to be appreciated, it would be desirable to provide a technique whereby the signals recorded on a recording medium may be identified from the signals themselves as being either original signals or copied signals without utilizing additional recording area for information which provides such indication.
A technique in which the digital information is buried in the picture information or the like is described in JP Patent Publication JP-A-6-315132 (1994) to Kokai. However, such technique may not be desirable in that the information can be packed.